Behaviour of price transmissions in vertically coordinated markets: The case of frozen black tiger shrimp (Penaeus monodon)*

Abstract

This study analyses the behaviour of the price transmission process for the leading cultured shrimp species, black tiger shrimp (Penaeus monodon), in both forward and backward directions between Thai and Indonesian shrimp packer markets and the Japan Tokyo wholesale market. The bivariate cointegration approach using the Engle‐Granger two‐stage estimation procedure is applied in this study. The results show that Tokyo wholesale prices appear to have stronger backward influences on the formation of overseas contract prices used by Japanese shrimp importers in the Thai and Indonesian shrimp packer markets. In addition, there is a tendency for the speed of price transmissions in the long term to increase with increasing size class (from 26 to 30–21–25 and 16–20 counts per pound) of black tiger shrimp, regardless of estimation specification in the direction of price transmissions and the shrimp country of origin.     

内蒙古白绒山羊褪黑激素受体基因SNP与产绒性状的关联

【目的】研究绒山羊褪黑激素受体（melatonin receptor,MTNR）基因的SNP与绒山羊产绒性状的关系,寻找可用于辅助选择的分子标记。【方法】以内蒙古阿尔巴斯型白绒山羊为研究对象,选择绒山羊褪黑激素受体（MTNR1a和MTNR1b）基因部分序列作为候选基因,采用PCR-SSCP分子标记技术和DNA测序技术研究其多态性,然后运用最小二乘方差分析方法,对各基因型间生产性状指标进行差异显著性检验。【结果】① 在绒山羊MTNR1a基因外显子1和2,以及MTNR1b基因外显子1没有检测到SSCP多态,而在绒山羊MTR1b基因外显子2中存在SSCP多态,首次检测到了3个SNP;② P4引物位点存在NM_001206907:g.648 bp处C-G突变,该突变没有导致氨基酸的改变;以及NM_001206907:g.665 bp处的G-A突变,该突变导致第223个密码子CGC变成CAC,从而使精氨酸变成组氨酸（Arg-His）;方差分析表明,该位点多态对绒山羊产绒量有显著影响（P＜0.05）;③AA基因型具有较高的产绒量,比AB、BB基因型产绒量分别高98.78和148.23 g,同时该多态位点基因型与年龄互作效应对绒山羊绒厚度有显著影响（P＜0.05）;④ P5引物位点存在NM_001206907:g.1 015 bp处的G-A突变,该突变导致第339个密码子GGC变成AGC,从而使甘氨酸变成丝氨酸（Gly-Ser）,分析表明该多态位点基因型与年龄互作效应对绒山羊绒细度存在边际显著影响（P＜0.1）;⑤ 这两个位点多态对绒山羊产羔数量、羔羊初生体重等繁殖性状均无显著影响（P＞0.05）。【结论】P4-AA基因型可以作为内蒙古阿尔巴斯型白绒山羊产绒量性状辅助选择的标记基因型。     

小麦矮秆种质山农矮330的农艺性状与矮化特性研究

调查分析了山农矮330的综合农艺性状及矮秆遗传特点。结果表明,山农矮330成穗能力强,小穗数多,结实性好,穗粒数多,且综合抗病性较好;携带一对不完全显性矮秆基因,对赤霉酸反应敏感,用其作矮秆亲本时致矮率在20％-30％,对后代的产量性状无明显的不利影响,其矮秆基因的表达受不同遗传背景的影响。     

高等教育与经济的关系--日本政策实践的视角

日本高等教育自2 0世纪90年代起开始全面改革,主要举措包括建立新的政府财政资助项目,选择性地分配经费;扩大研究生教育规模,突显研究型大学的作用;改革大学教育,加强大学与企业界的合作等。高等教育和经济的关系是高等教育改革的主旋律。     

2007年中国农村居民家庭纯收入和消费支出的多元回归分析

利用多元统计分析中的回归分析方法,建立了2007年我国农村居民家庭纯收入和消费支出的多元线性回归模型。根据回归结果,分析了2007年我国农村居民家庭纯收入和消费支出的内在关系,并对如何提高农村居民家庭收入水平和刺激消费提出了合理的建议。     

Scarce population genetic differentiation but substantial spatiotemporal phenotypic variation of water-use efficiency in <Emphasis Type="Italic">Pinus sylvestris</Emphasis> at its western distribution range

Water and carbon fluxes in forests are largely related to leaf gas exchange physiology varying across spatiotemporal scales and modulated by plant responses to environmental cues. We quantified the relevance of genetic and phenotypic variation of intrinsic water-use efficiency (WUE_i, ratio of net photosynthesis to stomatal conductance of water) in Pinus sylvestris L. growing in the Iberian Peninsula as inferred from tree-ring carbon isotopes. Inter-population genetic variation, evaluated in a provenance trial comprising Spanish and German populations, was low and relevant only at continental scale. In contrast, phenotypic variation, evaluated in natural stands (at spatial level) and by tree-ring chronologies (at temporal inter-annual level), was important and ten- and threefold larger than the population genetic variance, respectively. These results points to preponderance of plastic responses dominating variability in WUE_i for this species. Spatial phenotypic variation in WUE_i correlated negatively with soil depth (r?=???0.66; p?<?0.01), while temporal phenotypic variation was mainly driven by summer precipitation. At the spatial level, WUE_i could be scaled-up to ecosystem-level WUE derived from remote sensing data by accounting for soil water-holding capacity (r?=?0.63; p?<?0.01). This outcome demonstrates a direct influence of the variation of leaf-level WUE_i on ecosystem water and carbon balance differentiation. Our findings highlight the contrasting importance of genetic variation (negligible) and plastic responses in WUE_i (large, with changes of up to 33% among sites) on determining carbon and water budgets at stand and ecosystem scales in a widespread conifer such as Pinus sylvestris.     

An assessment of caprine tuberculosis prevalence in Lubumbashi slaughterhouse,Democratic Republic of Congo

Tropical Animal Health and Production - Caprine tuberculosis is a major health problem for goats and a major zoonosis of veterinary public health interest. In order to prepare a response to and...     

Assessment of the genetic diversity of Xylella fastidiosa in imported ornamental Coffea arabica plants

A study was performed in order to assess the presence of Xylella fastidiosa in imported ornamental plants, among them Olea europaea, Coffea arabica and Nerium oleander. Positive results were only obtained from C. arabica, where 15 plant samples tested positive for X. fastidiosa by PCR, nine from Costa Rica and six from Honduras. Transmission electron microscopy observations indicated that rod‐shaped bacterial cells exhibiting the characteristics of X. fastidiosa cells were present in the xylem vessels of leaf petioles obtained from the infected C. arabica plants. Diversity of X. fastidiosa in C. arabica plants was assessed through a multilocus sequence typing (MLST) analysis of seven housekeeping genes (leuA, petC, lacF, cysG, holC, nuoL and gltT) and compared with X. fastidiosa infecting different host plants worldwide. Based on this MLST analysis, the prevalence of different sequence types (STs) of X. fastidiosa in the C. arabica ornamental plants was demonstrated and related to different X. fastidiosa subspecies, underlining the risk of introducing additional genetic diversity for X. fastidiosa to Europe. ST53, related to X. fastidiosa subsp. pauca, was frequently found in these C. arabica samples. A second ST related to X. fastidiosa subsp. pauca, ST73, has been assessed in coinfection with ST53 in one individual plant. Additionally, ST72 and ST76, related to X. fastidiosa subsp. fastidiosa, have been recorded. Next to these previously described STs, a novel ST, namely ST77 has been revealed, related to X. fastidiosa subsp. fastidiosa. Isolation of X. fastidiosa from leaf petioles and midribs of infected C. arabica plants was successfully performed only after the application of an additional ultrasonication step during the extraction procedure. Based on this approach, a number of X. fastidiosa isolates were obtained and further characterized.     

Sequencing of Culex quinquefasciatus establishes a platform for mosquito comparative genomics

Culex quinquefasciatus (the southern house mosquito) is an important mosquito vector of viruses such as West Nile virus and St. Louis encephalitis virus, as well as of nematodes that cause lymphatic filariasis. C. quinquefasciatus is one species within the Culex pipiens species complex and can be found throughout tropical and temperate climates of the world. The ability of C. quinquefasciatus to take blood meals from birds, livestock, and humans contributes to its ability to vector pathogens between species. Here, we describe the genomic sequence of C. quinquefasciatus: Its repertoire of 18,883 protein-coding genes is 22% larger than that of Aedes aegypti and 52% larger than that of Anopheles gambiae with multiple gene-family expansions, including olfactory and gustatory receptors, salivary gland genes, and genes associated with xenobiotic detoxification.